flintgauge

Al Gore has posted numerous times on how global warming is true... so, i will try the experiment again in a lower gear... I'm all for the truth(global warming is not true). The reason I used 6th gear was to keep the car from slowing down as much as possible in order to get the longest distance out of each run.

My speed at the time was in fact 45 to 50 mph as dictated by the law. Coasting in neutral at 45 makes the readout show a theorectically infinite MPG, where as the slower speeds (in neutral)in turn yield a much lower readout (which is due to the fact that both times the engine is at idle but the speeds where different, making the higher speed much more efficient since the car will travel farther while burning the same amount as coasting at the lower speed).

The fact that the MPG was cut in half shows that the engine was still burning fuel during the coarse of engine and since it was half of what it was while coasting in neutral. I'm going to assume it was burning fuel at twice the rate required to maintain idle.

I fully understand and agree with the fact that engine compression and air drag are what cause engine braking, but you can engine brake while still on the throttle. It's not just that since the engine is burning no gas, as some would believe, it is however the fact that the engine is producing less power than is required to maintain the current speed of the vehicle, which creates "drag" on the wheels.

You could be going 60mph and floored in 6th gear, then down shift to 2nd or 3rd gear and only go 1/4 throttle, you will slow down, due to engine braking, but you are still burning gas, just as when you completely let off the throttle as well.

roast

iTrader: (2)

There are some incredibly stupid people on this forum.

flintgauge

and you are referring to who?

flintgauge

I after going back and re-reading your posts ROAST, I can tell you are a firm believer in Al Gore and all his disceptions. I know you must be mad, so go outside and hug a tree. I will make up for your fuel savings by going WOT from every stoplight tomorrow.

PS: yesterday I revved my engine at a prius next to me at a stop light and then busted out laughing. He just gave me the finger and took off. LOL

roast

iTrader: (2)

At least I can spell deception.

This wasn't a political debate, I was just making a point. If someones rebuttal is who cares, I say keep your ****in trap shut.

bailey bill

The engine isn't "running" but the crank is rotating, the pistons are stroking up and down, and valves are opening and closing.

Turn the ignition off at 60 MPH and leave it in gear. .. Is the engine running?...Nope. Is it using fuel?...Nope. But the engine is definitely spinning...and the car is still moving. Shutting the engine off does NOT lock up the rear tires, it just creates engine braking.

Yes, you could leave it gear and have a tow truck drag you around town, and the car being towed would NOT use any fuel. The tires turn the axles, the axles turn the driveshaft, the driveshaft turns the tranny, and the tranny turns the engine crankshaft. Haven't you ever "push-started" a car?

An engine needs fuel to run, but it can still pump air in and air out withiut any fuel being introduced. And that pumping action creates the compression that provides engine braking.

bill

Matt8200

The planet has been getting warmer for the past 25,000 years. Is CO2 the cause...no, but that is another topic.

350Zenophile

iTrader: (20)

It is not a fuel gauge, it's a trip meter. If you want to present a scientific test to prove your hypothesis, you need to present an exact understanding of how it calculates average fuel consumption. Since none of us are privy to that information any use of it in a test nullifies the results of the test.

350Zenophile

iTrader: (20)

I found this is the 350Z Service Manual:

I put the note above in bold, because the example given above is regarding shift position in Neutral. When shift position is other than in neutral (in gear) that is referred to as deceleration control (i.e. engine braking). So we reference EC-25:

Not sure it can be any clearer than that. End of Debate. Close thread.

Now let's all go back to driving our cars for fun.

EddNog

Does it state anywhere the exact RPM at which idle fuel kicks back in when in gear? It's hard to tell from feel; I do feel it, but it's a bit vague being such a small amount of fuel.

-Ed

350Zenophile

iTrader: (20)

I can feel it kick back in between 1200-1500rpm so I have no reason to believe it wouldn't follow suit with the Fuel Cut Control quote listed above: "Fuel cut will be operated until the engine speed reaches 1,500 rpm, then fuel cut will be cancelled."

bailey bill

Authoratative, well-documented information is always a valuable contribution to discussions. Thank you.

bill

350Zenophile

iTrader: (20)

One Quick Z

iTrader: (8)

I concur with all those who believe that fuel is shut off during engine braking.

You can verify this with a wideband O2 sensor gauge like I have. When you let off the gas the wideband pegs lean because there is no fuel in the mixture.

Also if you've ever owned a car that you can datalog, you'll notice that your injector duty cycle goes to 0% during engine braking.

I just thought I'd add those two things for the people that like to see real world proof instead of text book proof.

bailey bill

Excellent info also. Thanks for posting it

bill

Blue Liquid

That seems pretty authoritative. Matt, ROAST, what do you guys think? Backs up your arguments, I would think.

Kolia

iTrader: (2)

Another engine braking vs fuel economy thread ?

I'm amazed I missed that one aha !

Miko

iTrader: (2)

Coasting in gear to a stop light from 200+ meters away as if trying to catch the next wave is the way one can get 29.x MPG or 500+ dte in the city. It also involves gentle acceleration and shifting at 2000 RPMs. Be warned that the 1-2 shift (waiting for the RPMs to drop) will probably **** people off behind you, as will the coasting in gear from such distances. I think it may earn oneself a ticket too I belive.

roast

iTrader: (2)

You would think. I wouldn't be at all surprised if another person comes in here saying how much gas he saves by idling.

So what is all dis turbonator hype? Will it really double the powah to muh dubs? I want vtach installed too. Anyone know where I can get it?

I provided not one, not two, but three real world examples that anyone with a Z can perform to prove the point. Another member graciously posted documentation from the service manual that further proves the point. What more could you ask for? I'll let them use my toilet, but I won't be wiping anyones ***.

gsazabi

iTrader: (51)

Only time my car's in neutral is when it's stuck in traffic/stop light